On Wed, 02 Oct 2024 14:31:13 +0000
"Arnd Bergmann" [off-list ref] wrote:

On Wed, Oct 2, 2024, at 12:41, Herve Codina wrote:

quoted

On Wed, 02 Oct 2024 11:08:15 +0000
"Arnd Bergmann" [off-list ref] wrote:  

quoted

On Mon, Sep 30, 2024, at 12:15, Herve Codina wrote:
  

quoted

+			pci-ep-bus@0 {
+				compatible = "simple-bus";
+				#address-cells = <1>;
+				#size-cells = <1>;
+
+				/*
+				 * map @0xe2000000 (32MB) to BAR0 (CPU)
+				 * map @0xe0000000 (16MB) to BAR1 (AMBA)
+				 */
+				ranges = <0xe2000000 0x00 0x00 0x00 0x2000000
+				          0xe0000000 0x01 0x00 0x00 0x1000000>;    

I was wondering about how this fits into the PCI DT
binding, is this a child of the PCI device, or does the
"pci-ep-bus" refer to the PCI device itself?  

This is a child of the PCI device.
The overlay is applied at the PCI device node and so, the pci-ep-bus is
a child of the PCI device node.  

Ok

quoted

				/*
				 * Ranges items allow to reference BAR0,
				 * BAR1, ... from children nodes.
				 * The property is created by the PCI core
				 * during the PCI bus scan.
				 */
				ranges = <0x00 0x00 0x00 0x82010000 0x00 0xe8000000 0x00 0x2000000
					  0x01 0x00 0x00 0x82010000 0x00 0xea000000 0x00 0x1000000
					  0x02 0x00 0x00 0x82010000 0x00 0xeb000000 0x00 0x800000  

quoted

Hope this full picture helped to understand the address translations
involved.  

Right, that makes a lot of sense now, I wasn't aware of those
range properties getting set. Now I have a new question though:

Is this designed to work both on hosts using devicetree and on
those not using it? If this is used on devicetree on a board
that has a hardwired lan966x, we may want to include the
overlay contents in the board dts file itself in order to
describe any possible connections between the lan966x chip
and other onboard components such as additional GPIOs or
ethernet PHY chips, right?

      Arnd

On host with the base hardware described without device-tree (ACPI on
x86 for instance), I have a couple of patches not yet sent upstream.
With those patches, I have a the LAN966x PCI board working on x86.
I plan to send them as soon as this series is applied.

Rob said that before looking at ACPI, we need to have a working system
on DT based systems.
  https://lore.kernel.org/all/CAL_JsqKNC1Qv+fucobnzoXmxUYNockWR=BbGhds2tNAYZWqgOA@mail.gmail.com/ (local)

If hardwired on a board, the same LAN966x PCI driver could be used.
A possible improvement of the driver could be to request the overlay
from the user-space using request_firmware().
With that, the overlay can be extended with specific onboard parts the
LAN966x PCI device is connected to.

This improvement can be done later when the use case appears.

Best regards,
Hervé